In his lab at the Bayerisches Geoinstitut in Germany, Dan Frost is trying to simulate conditions found in the Earth's lower mantle. More than 1,800 miles below the surface, the lower mantle experiences temperatures nearing 4,000 degrees Fahrenheit and pressures that are 1.3 million times higher than the air we breathe.

According to David Robson at BBC Future, in trying to simulate those scorching underground environments, Frost has stumbled upon some innovative ways to manufacture diamonds. Beneath their sparkles, diamonds are composed of simple carbon atoms arranged into a crystal.

Frost's research started with a hypothesis that in ancient times, rocks could have pulled carbon dioxide from the oceans. Then, as the rocks were drawn down into the mantle, high pressures force the CO2 to leave the rocks. Once the CO2 was free, iron in the mantle stripped it of its oxygen. That left just the naked carbon, which was squished into diamond by the high heat and temperatures. That was the hypothesis anyway, "[a]nd that is exactly what Frost found when he recreated the process using his presses – essentially forging a diamond from thin air," writes Robson.

Because all foodstuffs (and for that matter, all living things) contain carbon, the researchers have successfully made diamonds out of everyone's favorite sandwich ingredient: peanut butter. However, the hydrogen that's bonded to the carbon in peanut butter apparently does make the process messier. And even under the best circumstances, the transformation is slow. "If we wanted a two-or-three-millimetre diamond, we would need to leave it for weeks," Frost told BBC Future.